Here it is said http://blogs.iis.net/webtopics/archive/2010/04/27/configuring-many-to-one-client-certificate-mappings-for-iis-7-7-5.aspx
Many-to-one Client certificate mapping is used by the Internet Information Services (IIS) to associate an end user to a windows account when the client certificate is used for the user authentication.
What if I don't want to map with a windows account but with an account in custom database or in membership ?
How to do it in asp.net (sample code somewhere ?)
hmm: nobody knows ? Will have to give bounty soon :)